Intrinsic Defect Chemistry of High-Voltage LiMn1.5Ni0.5O4 (LMNO) Spinel Cathode

Abstract

High-voltage spinel LiMn1.5Ni0.5O4 (LMNO) can exist in a Mn/Ni ordered P4_332 or disordered Fd-3m arrangement with a majority of literature studies reporting improved electrochemical performance for the disordered phase. Through modifying synthesis conditions, the Mn/Ni ordering can be tuned, however oxygen and Mn3+ stoichiometries are also affected, making it difficult to decouple these responses and optimise performance. Here, we investigate all intrinsic defects in P4_332 LMNO under various growth conditions, using density functional theory (DFT) calculations. We find that the majority of defects are deep and associated with small polarons (Mn3+, Mn2+ and Ni3+) formation. The tendency for cation disorder can be explained by the low formation energy of the antisite defects and their stoichiometric complexes. The intrinsic Fermi level of LMNO varies from moderately n-type under oxygen-poor conditions to weakly p-type under oxygen-rich conditions. Our work explains experimental observations (e.g. the Mn/Ni disorder) and provides guidelines for defect-controlled synthesis.

Recent Progress of High Voltage Spinel LiMn1.5Ni0.5O4 Cathode Material for Lithium-Ion Battery: Surface Modification, Doping, Electrolyte, and Oxygen Deficiency

“…In addition, several anode materials have been paired with LMNO to study the full cell characteristics. − Among these materials, Li 4 Ti 5 O 12 (LTO), operating at 1.5 V, has gained interest because when it is paired with LMNO cathode, it exhibits a safer and higher power battery with superior electrochemical performance at a voltage window of 3.2 V. ,− Likewise, in recent years, optimization of LMNO has been studied, such as defect studies by using density functional theory (DFT) to understand the structure of ordered ( P 4 3 32) and disordered ( Fd m ) phase. These studies focus on understanding the effects of defects on the ordered and disordered phases. − Moreover, LMNO has the advantages of being inexpensive, easy to synthesize, and having 3D spinel structures that allow rapid Li-ion diffusion. , …”